Electromagnetic valve

ABSTRACT

A pilot valve element includes a metallic pilot valve body formed integrally with a plunger, a flexible sealing member, fitted on a tip of the pilot valve body, which touches and leaves a pilot valve seat, and a stopper for restricting the displacement of the pilot valve element relative to a driven member in a manner such that the sealing member is stopped in a direction of axis line after the sealing member has seated on a pilot valve seat. The stopper is configured such that the pressure-receiving diameter of the sealing member, which receives a pressure difference between an upstream side and a downstream side of the pilot valve, remains unchanged from when the sealing member comes in contact with the pilot valve seat until when the sealing member is stopped by the stopper with the result that the sealing member has completely seated on the pilot valve seat.

CLAIM OF PRIORITY TO RELATED APPLICATION

The present application is claiming priority of Japanese PatentApplication No. 2013-198855, filed on Sep. 25, 2013, the content ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pilot operated electromagnetic valve.

2. Description of the Related Art

An automotive air conditioner is generally configured such that itincludes a compressor, a condenser, an evaporator, and so forth arrangedin a refrigerant circulation passage. Various types of control valvesare provided for the purpose of, for example, switching the refrigerantcirculation passages according to the operation state in such arefrigeration cycle and regulating the flow rate of refrigerant. A pilotoperated electromagnetic valve capable of controlling the opening andclosing of a large valve section using a relatively small electric powermay be used as such the control valve (see Reference (1) in thefollowing Related Art List, for instance).

Such an electromagnetic valve drives a small pilot valve element by asolenoid so as to open and close a pilot valve and then drives a largemain valve element by a pressure difference regulated thereby so as toopen and close a main valve. A piston is formed integrally with the mainvalve element, and a back pressure chamber is formed by this piston as aseparated space inside a body. A leak passage through which to introducethe refrigerant into the back pressure chamber, and a pilot passagethrough which the refrigerant is led out from the back pressure chamber,are formed in the main valve element. And the opening and closing of thepilot valve opens and blocks the pilot passage, respectively. With thisstructure, the opening and closing of the main valve is controlled byvarying the pressure of the back pressure chamber. The pressure of theback pressure chamber is regulated through a balance between the flowrate of refrigerant introduced into the back pressure chamber and theflow rate of refrigerant led out from the back pressure chamber.

2. Related Art List

-   (1) Japanese Unexamined Patent Application Publication (Kokai) No.    2001-124440.

As one of such electromagnetic valves, there is available a valve wherea flexible sealing member, such as rubber, is placed at a tip of thepilot valve element to ensure the sealing property of the pilot valveand where the pilot valve element touches and leaves a pilot valve seatprovided in the main valve element. By employing such a configuration asdescribed above, the sealing member is appropriately deformed and thenadheres tightly to the pilot valve seat when the sealing member seats onthe pilot valve seat. Thereby, excellent sealing property can beachieved. Nevertheless, the pilot valve element is formed integrallywith a movable iron core of the solenoid and therefore such adeformation may adversely affects the stroke of the movable iron core.In other words, the stroke of the movable iron core varies depending ona deformation amount of the sealing member and therefore the magneticgap between the movable iron core and a fixed iron core varies. This mayadversely affect the control performances of the solenoid. In somecases, the movable iron core and the fixed iron core hit each other andthis may possibly cause noise. Also, depending on the shape of the pilotvalve seat, the pressure-receiving diameter of the sealing memberchanges as a result of a change in the stroke of the pilot valve elementand then the balance between a pressure difference exerted, between anupstream side and a downstream side of the pilot valve element, and thesuction force of the solenoid is lost. This may also adversely affectthe control performances.

SUMMARY OF THE INVENTION

A purpose of the present invention is to stabilize the controlcharacteristics in opening and closing a pilot generated electromagneticvalve while the sealing property of a pilot valve is kept.

In order to resolve the aforementioned problems, an electromagneticvalve is a pilot operated electromagnetic valve and it includes: a bodyhaving a lead-in port through which a fluid is led in, a lead-out portthrough which the fluid is led out, and a main passage joining thelead-in port to the lead-out port; a metallic driven member integrallyformed with both a main valve element and a partition, wherein the mainvalve element opens and closes a main valve by touching and leaving amain valve seat provided in the main passage and wherein the partitionseparates the main passage from a back pressure chamber; a pilot valveelement that opens and closes a pilot valve by touching and leaving apilot valve seat, the pilot valve seat being provided in a sub-passagejoining the lead-in port to the lead-out port with the back pressurechamber arranged between the lead-in port to the lead-out port; and asolenoid including a first iron core, which is displaced integrally withthe pilot valve element in a direction of axis line, and a second ironcore, which is disposed in a position axially opposite to the first ironcore in the direction of axis line. A pilot passage is formed in suchmanner as to pass through the driven member; the pilot valve seat isprovided at one end side of the pilot passage such that the pilot valveseat protrudes toward the back pressure chamber; and the other end ofthe pilot passage communicates with the lead-out port. And the pilotvalve element includes: a metallic pilot valve body formed integrallywith the first iron core; a flexible sealing member, fitted on a tip ofthe pilot valve body, which touches and leaves the pilot valve seat; anda stopper for restricting a displacement of the pilot valve elementrelative to the driven member in a manner such that the stopper isstopped in the direction of axis line after the sealing member hasseated on the pilot valve seat. The stopper is configured such that apressure-receiving diameter of the sealing member, which receives apressure difference between an upstream side and a downstream side ofthe pilot valve, remains unchanged from when the sealing member comes incontact with the pilot valve seat until when the sealing member hascompletely seated on the pilot valve seat with the result that thestopper is stopped by the driven member.

By employing this embodiment, when the pilot valve element seats on thepilot valve seat, the sealing member gets deformed and thereby theexcellent sealing property remains in effect. Also, the stopper isstopped after the sealing member has seated on the pilot valve seat,thereby restricting the displacement of the pilot valve element. Thus,the magnetic gap of the solenoid can be kept constant. Also, thepressure-receiving diameter while the pilot valve element is seating isconstantly kept at a fixed diameter. This can prevent the first ironcore and the second iron core from hitting each other and thereforeprevents the noise that may otherwise occur in the event that the firstiron core and the second iron core hit each other. Also, the controlperformances by the solenoid are stabilized.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described by way of examples only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures in which:

FIG. 1 is a cross-sectional view showing a concrete structure of anelectromagnetic valve according to an embodiment;

FIG. 2 is a diagram for explaining an operating state of a controlvalve;

FIG. 3 is a partially enlarged view showing a fall prevention structureof a sealing member in a valve element;

FIG. 4 schematically shows a process of assembling a sealing member;

FIGS. 5A and 5B each shows a structure of a support member before thesupport member is assembled;

FIGS. 6A and 6B are each a partially enlarged view of a seal structurein a piston of a driven member;

FIGS. 7A and 7B are each a perspective view showing a structure of acomponent of a piston;

FIG. 8 is a graph showing an operation and advantageous effects of aseal structure in a piston;

FIGS. 9A and 9B are each a partially enlarged view showing a stopperstructure in a pilot valve; and

FIGS. 10A and 10B are each a partially enlarged view showing a structureof a seal structure in a piston of a driven member according to amodification.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described by reference to the preferredembodiments. This does not intend to limit the scope of the presentinvention, but to exemplify the invention.

The present invention will now be described in detail based on preferredembodiments with reference to the accompanying drawings. In thefollowing description, for convenience of description, the positionalrelationship in each structure may be expressed with reference to howeach structure is depicted in Figures. The present embodiment is aconstructive reduction to practice of the present invention where acontrol valve according to the preferred embodiments is used as anelectromagnetic valve applied to an air conditioner of anelectric-powered vehicle. The automotive air conditioner is providedwith a refrigeration cycle wherein a compressor, an internal condenser,an external heat exchanger, an evaporator, and an accumulator areconnected to each other by piping. The automotive air conditioner isconfigured as a heat pump type air conditioner that performs airconditioning inside a vehicle's passenger compartment using the heat ofrefrigerant in a process where the refrigerant, which is used as aworking fluid, circulates within the refrigeration cycle while therefrigerant changes its state. The automotive air conditioner operatesin such a manner as to switch a plurality of refrigerant circulationpassages at the time of cooling and heating. The control valve accordingto the present embodiment is provided at a branch point of theserefrigerant circulation passages and is configured as a three-way valvethat switches the flows of refrigerant.

A description is now given of a concrete structure of the control valveaccording to the present embodiment. FIG. 1 is a cross-sectional viewshowing a concrete structure of an electromagnetic valve according to anembodiment.

A control valve 1, which is a so-called pilot operated electromagneticvalve, is configured by assembling a valve unit 2 and a solenoid 4 in adirection of axis line. A main valve 6 and a pilot valve 8 are builtinto a body 5 of the valve unit 2. Here, the main valve 6 switches theflow of refrigerant from an upstream passage to either a firstdownstream passage or a second downstream passage, and the pilot valve 8controls the opening and closing of the main valve 6.

The body 5 is configured such that a second body 12 of steppedcylindrical shape and a third body 13 of stepped cylindrical shape areassembled inside a first body 10, which is a prismatic column in shape.In the present embodiment, the first body 10 and the second body 12 areeach made of an aluminum alloy, and the third body 13 is made ofstainless steel (SUS). A lead-in port 14 leading to the upstream passageis provided on one of side surfaces of the first body 10. A lead-outport 16 (corresponding to “first lead-out port”) leading to the firstdownstream passage is provided on an upper portion of a side opposite tosaid one of side surfaces of the first body 10, whereas a lead-out port18 (corresponding to “second lead-out port”) leading to the seconddownstream passage is provided on a lower portion thereof.

The second body 12 has a stepped cylindrical body with the diameterreduced toward the bottom, and the second body 12 is coaxially held bythe first body 10. An O-ring 20 is fitted on the outer periphery of anupper end of the second body 12, and an O-ring 22 is fitted on the outerperiphery of a lower end thereof. Provision of the O-ring 20 and theO-ring 22 prevents the refrigerant from being leaked through a gap inbetween the first body 10 and the second body 12. A valve hole 26(corresponding to “first valve hole”) is formed in the lower end of thesecond body 12, and a valve seat 28 (corresponding to “first valveseat”) is formed in a lower end opening of the valve hole 26. Acommunication hole 30, which communicates to and from the second body12, is formed in a surface facing the lead-out port 16 of the secondbody 12. A first passage (corresponding to “first main passage”) joiningthe upstream passage to the first downstream passage is formed by aninternal passage that connects the lead-in port 14, the valve hole 26and the lead-out port 16.

The third body 13 of stepped cylindrical shape is held in an upperportion of the first body 10. An O-ring 27 is set between an upper endof the first body 10 and the third body 13. Provision of the O-ring 27prevents the refrigerant from being leaked through a gap in between thefirst body 10 and the third body 13. The diameter of the third body 13in an upper half thereof is reduced, and a reduced diameter portionthereof functions as a connection area where the solenoid 4 and thethird body 13 are connected. An O-ring 29 is fitted on the outerperiphery of an upper end of the third body 13.

A valve seat forming section 32 having a circular boss shape is providedin a communicating area, where the lead-in port 14 and the lead-out port18 meet and communicate with each other, in the first body 10. The valveseat forming section 32 protrudes on a second body 12 side, and a valvehole 34 (corresponding to “second valve hole”) is formed in a spaceinward from the valve seat forming section 32. A valve seat 36(corresponding to “second valve seat”) is formed by an upper-end openingedge of the valve seat forming section 32. A second passage(corresponding to “second main passage”) joining the upstream passage tothe second downstream passage is formed by an internal passage thatconnects the lead-in port 14, the valve hole 34 and the lead-out port18. The valve hole 26 and the valve hole 34 are provided in the coaxialdirection, and a valve chamber 38 is formed between the valve hole 26and the valve hole 34.

A driven member 40 is disposed inside the body 5. The driven member 40is comprised of a cylindrical body 42, a valve element 44 integrallyformed with the body 42 at a lower end of the body 42, a piston 46formed integrally with body 42 at an upper portion thereof, and apartition member 48. Here, the cylindrical body 42 extends along acentral portion of the body 5 in the direction of axis line, and thepartition member 48 is provided in a middle part of the body 42 in thedirection of axis line such a manner as to protrude radially outward. Inthe present embodiment, the body 42 is made of an aluminum alloy. Thebody 42 is so provided as to penetrate the second body 12. A pilotpassage 50 is so provided as to run through the body 42 in the directionof axis line. A pilot valve hole 49 is formed such that the insidediameter of an upper end of the body 42 is slightly reduced, and a pilotvalve seat 51 is formed on an upper end opening of the pilot valve hole49.

The valve element 44 includes a support member 52 and a guide member 54,which are inserted around and secured to the lower end of the body 42, apacking material 56 (which functions as “first sealing member”)supported by a top face of the support member 52, and a packing material58 (which functions as “second sealing member”) supported by a bottomface of the support member 52. In the present embodiment, the supportmember 52 and the guide member 54 are each made of stainless steel(SUS). The packing materials 56 and 58 are each formed of a ring-shapedelastic body (e.g., rubber in the present embodiment). The valve element44, which is displaceable within the valve chamber 38, closes and opensa first valve section when the packing material 56 touches and leavesthe valve seat 28, respectively. Similarly, the valve element 44 closesand opens a second valve section when the packing material 58 touchesand leaves the valve seat 36, respectively. Note that the valve element44 is provided with fall prevention structures, which are used toprevent the packing materials 56 and 58 from falling off. A detaileddescription of the fall prevention structures will be discussed later.

The guide member 54 has a disk-shaped body, which supports the supportmember 52 from below, and a plurality of legs 60 (only one of these legsshown in FIG. 1), which extend downward from a peripheral edge part ofthis disk-shaped body. And the guide member 54 is slidably supported byand along an inner circumferential surface of the valve hole 34. Acylindrical strainer 62 is provided in the valve chamber 38 in such amanner as to surround the valve element 44 from outside. The strainer 62includes a filter that suppresses foreign materials from entering thevalve chamber 38.

A piston 46 functions as a “partition member” by which a spacesurrounded by the second body 12 and the third body 13 is partitionedinto a high-pressure chamber 64 and a back pressure chamber 66. Thehigh-pressure chamber 64 communicates with the lead-in port 14 by way ofa communicating path 67. The back pressure chamber 66 communicates withthe inside of the solenoid 4. A “sub-passage” is constituted by apassage that communicates the lead-in port 14 to the lead-out port 18 byway of the communicating path 67, the high-pressure chamber 64, the backpressure chamber 66 and the pilot passage 50. The piston 46 is slidablysupported by and along a guiding passage 73, which is formed in an innercircumferential surface of the third body 13. The driven member 40 isconfigured such that a piston ring 72 and the legs 60 are slidablysupported by and along an inner circumferential surface of the body 5.This configuration allows the driven member 40 to operate in astabilized manner in the opening and closing directions of the valvesection.

The piston 46 is configured such that the piston 46 is divided, alongthe direction of axis line, into a piston body 68 and a support 70 andsuch that the piston ring 72 is held between the piston body 68 and thesupport 70. In the present embodiment, the piston body 68 and thesupport 70 are each made of an aluminum alloy, and the piston ring 72 isformed of polytetrafluoroethylene (PTFE). The piston body 68 is ofstepped disk shape such that the diameter thereof is reduced in stagestoward the bottom. And the piston body 68 is secured such that thepiston body 68 is coaxially press-fitted to an upper portion of the body42. A leakage passage 74, having a small diameter, through which thehigh-pressure chamber 64 and the back pressure chamber 66 communicatewith each other is formed in the piston body 68. A flange portion, whichextends radially outward and abuts against a top face of the piston ring72, is provided at an upper end of the piston body 68.

The support 70, which is of stepped annular shape, is fitted to a lowerhalf of a smaller-diameter part of the piston body 68 in such a manneras to be inserted around the lower half thereof. A flange portion, whichextends radially outward and abuts against a bottom face of the pistonring 72, is provided at an upper end of the support 70. A spring 76,which biases the piston 46 in an upward direction, is set between thesupport 70 and the second body 12. The spring 76 functions as a “biasingmember” that biases the support 70 in a direction in which the support70 is brought close to the piston body 68. The outside diameter of eachof the flange portions of the piston body 68 and the support 70 isslightly smaller than the inside diameter of the guiding passage 73.

The piston ring 72 is assembled between the piston body 68 and thesupport 70 in a manner such that the piston ring 72 is fitted into arecess formed by the piston body 68 and the support 70. A tension ring78 is set between an outer circumferential surface of the piston body 68and an inner circumferential surface of the piston ring 72. The tensionring 78, which is formed of a spring steel, biases the piston ring 72radially outward from the inside of the piston ring 72. Thereby, thepiston ring 72 is pressed against the guiding passage 73 so as to obtainan appropriate sliding resistance. In other words, the piston 46 isslidably supported by and along the guiding passage 73 at the positionof the piston ring 72. Though, in the present embodiment, the sealingproperty is improved using a specially assembled structure, its detaileddescription will be given later.

A pressure-receiving regulation member 53 is provided in an upper endopening of the second body 12. The pressure-receiving regulation member53 regulates an effective pressure-receiving area of the partitionmember 48 such that when the first valve section is closed, thepressure-receiving regulation member 53 attaches firmly to the partitionmember 48. The pressure-receiving regulation member 53 is formed of aring-shaped thin elastic body (e.g., rubber). A stopper ring 55 ispress-fitted to an upper end of the second body 12. Thepressure-receiving regulation member 53 is supported such that athick-walled part in the outer periphery thereof is held between thesecond body 12 and the stopper ring 55.

The solenoid 4 has a stepped cylindrical core 80 (fixed iron core),which is assembled to the third body 13 on an upper end thereof, and abottomed cylindrical sleeve 82, which is so assembled as to contain anupper portion of the core 80. Assembling the sleeve 82, which isnonmagnetic to the core 80, constructs a can for closing an internalpressure chamber. A cylindrical plunger 84 (movable iron core) iscontained in the sleeve 82. A plunger 84 is disposed within the sleeve82 in a position axially opposite to the core 80 in the direction ofaxis line. A back pressure chamber 85 is formed between the bottom ofthe sleeve 82 and the plunger 84.

A ring-shaped fixed member 86 is fastened in an upper end opening of thefirst body 10. Thereby, the core 80 is secured relative to the thirdbody 13. In other words, a flange portion, which protrudes radiallyoutward, is provided at a lower end of the core 80, and a fittingrecess, which has a shape that is complementary to the shape of theflange portion, is formed at a lower end of the fixed member 86. Also,the fixed member 86 has an external thread on an outer peripherythereof, and an internal thread is formed in an upper end opening of thefirst body 10. Thus, the core 80 can be stably secured when the fixedmember 86 is screwed to the first body 10 while a lower end of the core80 is being inserted around the upper end of the third body 13. TheO-ring 29 is set between the core 80 and the third body 13, andprovision of the O-ring 29 prevents the refrigerant from being leakedthrough a gap in therebetween.

A bobbin 88 is provided on an outer periphery of the sleeve 82, and anelectromagnetic coil 90 is wound around the bobbin 88. A pair of endmembers 92 are so provided as to hold the electromagnetic coil 90 fromtop and bottom thereof. The end members 92 also function as a yoke thatconstitutes a magnetic circuit. The can penetrates the pair of endmembers 92 in the direction of axis line. A current carrying harness(not shown) is led out from the electromagnetic coil 90.

A guide member 94, which protrudes radially inward, is provided in acentral part of the core 80 in the direction of axis line. A taperedsurface, where the inside diameter of the core 80 is larger upward, isformed at an upper end of the core 80. Also, a tapered surface where theoutside diameter of the plunger 84 is smaller downward, is formed at alower end of the plunger 84. A small-diameter part 95, which is insertedto and removed from the core 80, is provided in a lower-end center partof the plunger 84. In other words, the surface of the plunger 84 facingthe core 80 and the surface of the core 80 facing the plunger 84 are thetapered surfaces each having a shape complementary to that of the other.Moreover, the arrangement is such that a part of the plunger 84 can beinserted to and removed from the core 80. Thus, a large stroke of theplunger 84 is secured and, at the same time, a sufficient magneticattractive force is obtained. Also, a relatively large recessed groove96 is formed on an outer circumferential surface of the small-diameterpart 95, thereby in habiting the magnetic leakage of the plunger 84 andthe core 80 in a radial direction. By employing such configuration andarrangement as described above, the suction force produced by thesolenoid 4 is obtained efficiently and stably.

A fitting hole 100 used to couple a pilot valve element 98 is formed ina lower half of the plunger 84. Also formed are a communicating path102, which runs through the plunger 84 in the direction of axis line, acommunicating path 104, which runs through the plunger 84 in a radialdirection, and a communicating groove 106 in parallel with the axis linealong an outer circumferential surface of the plunger 84. Thecommunicating paths 102 and 104, the communicating groove 106, and thefitting hole 100 communicate with one another. By employing suchstructure and arrangement as described above, a state of communicationbetween a space, between the core 80 and the plunger 84, and the backpressure chamber 85 is maintained. Set between the core 80 and theplunger 84 is a spring 108 (functioning as a “biasing member”) thatbiases the core 80 in such a direction as to separate the core 80 awayfrom the plunger 84.

The pilot valve element 98 has a body 110 of stepped cylindrical shape,and a sealing member 112 is fixed to a lower end of the body 110. Anupper end of the body 110 is press-fitted to the lower end of theplunger 84 and thereby the pilot valve element 98 and the plunger 84 arecoaxially integrated with each other. The body 110 penetrates the guidemember 94 of the core 80. A lower end part of the body 110 is a valveformation part 114 having a slightly large diameter, and this valveformation part 114 is located in the back pressure chamber 66. Arecessed fitting space 116 is formed at a lower end of the valveformation part 114, and a disk-shaped sealing member 112 is fittedthere. In the present embodiment, the body 110 is made of stainlesssteel (SUS) and the sealing member 112 is made of rubber. The sealingmember 112 is immovably supported such that the lower end of the valveformation part 114 is swaged inward. The pilot valve 8 is closed andopened when the sealing member 112 of the pilot valve element 98 touchesand leaves the pilot valve seat 51, respectively. A caulking part of thevalve formation part 114, where the lower end thereof is swaged inward,constitutes a stopper 118, which is stopped by an upper end of thedriven member 40. A detailed description of the stopper 118 will begiven later.

Formed in the body 110 are a communicating path 120, which runs over anarea starting from an upper end of the body 110 up to the fitting space116 in the direction of axis line, and a communicating path 122, whichruns through the valve formation part 114 in the radial direction. Thecommunicating path 120 and the communicating path 122 communicate witheach other inside the valve formation part 114. By employing suchstructure and arrangement as described above, the internal space of thesolenoid 4 (i.e., a space, between the core 80 and the plunger 84, andthe back pressure chamber 85) and the back pressure chamber 66communicate with each other. In other words, the pressure of the backpressure chamber 66 is stably supplied to the internal space of thesolenoid 4.

An O-ring 124 is fitted to an upper portion of the valve formation part114. The O-ring 124 functions as a “shock-absorbing member”. That is, asthe conduction state (on/off state) of the solenoid 4 is switched fromthe conducting state to the nonconducting state (from on to off), theplunger 84 is displaced in the upward direction along the direction ofaxis line as shown in FIG. 1. However, the displacement of the plunger84 is restricted when the core 80 stops the O-ring 124. The O-ring 124,which functions as the shock-absorbing member, deforms when the O-ring124 is stopped by the core 80, thereby absorbing the shock. As a result,the occurrence of hitting sound is suppressed as compared with the casewhen the plunger 84 is directly stopped by the sleeve 82 on the bottomface thereof.

Also, such the shock-absorbing member is provided in the pilot valveelement 98, that is, the shock-absorbing member is not provided in anyof the components of the solenoid 4, such as the core 80, the sleeve 82and the plunger 84. This can prevent the shock-absorbing member frombeing thermally deformed and prevent the physical property thereof frombeing altered. In other words, the core 80 and the sleeve 82 areassembled together such that the core 80 and the sleeve 82 are weldedtogether while the plunger 84 is being contained inside the sleeve 82;as a result, the shock-absorbing member may possibly be deformed underthe influence of the welding heat if the shock-absorbing member isprovided in any of the core 80, the sleeve 82 and the plunger 84. Inconsideration of the above fact, the shock-absorbing member is providedin the pilot valve element 98, in the present embodiment. Hence, theincident of the shock-absorbing member being deformed and the like canbe avoided. The pilot valve element 98 can be press-fitted to the sleeve82 after the welding of the core 80 and the sleeve 82 has beencompleted.

In the above-described structure and arrangement, an upstream-sidepressure P1 introduced from the lead-in port 14 (hereinafter referred toas “upstream-side pressure P1”) becomes a pressure P2 (hereinafterreferred to as “downstream-side pressure P2”) by passing through themain valve 6 in the first passage. At the same time, the upstream-sidepressure P1 becomes a pressure P3 (hereinafter referred to as“downstream-side pressure P3”) by passing through the main valve 6 inthe second passage. Also, the upstream-side pressure P1 is led into thehigh-pressure chamber 64 after passing through the communicating path67, then becomes an intermediate pressure Pp at the back pressurechamber 66 by passing through the leakage passage 74, and furtherbecomes the downstream-side pressure P3 by passing through the pilotvalve 8.

According to the present embodiment, an effective pressure-receivingdiameter A (seal section diameter) of the valve hole 26 and an effectivepressure-receiving diameter B (seal section diameter) of the partitionmember 48 are set equal to each other. Thus, the effect of thedownstream-side pressure P2 acting on the driven member 40 is cancelled.In particular, provision of the pressure-receiving regulation member 53strictly achieves the cancellation of the effect of the downstream-sidepressure P2 acting thereon. In other words, when the first valve sectionis closed as shown in FIG. 1, a bottom face of the pressure-receivingregulation member 53 and a top face of the partition member 48 attachfirmly to each other. This achieves the accurate pressure cancellation.

The control valve 1 configured as described above functions as a pilotoperated control valve that switches the flow passages of refrigerant,depending on the conduction state of the solenoid 4. An operation of thecontrol valve 1 is hereinbelow described in detail. FIG. 2 is a diagramfor explaining an operating state of a control valve 1. FIG. 2represents a conducting state where the solenoid 4 is turned on. Notethat the already-explained FIG. 1 represents a nonconducting state wherethe solenoid 4 is turned off.

Since, as shown in FIG. 1, the solenoidal force does not work while thesolenoid 4 is turned off, the pilot valve element 98 is biased, by thespring 108, in a valve opening direction and therefore the pilot valve 8is open. At this time, the refrigerant at the back pressure chamber 66is led out to a downstream side through the pilot passage 50 andtherefore the intermediate pressure Pp drops. Hence, the driven member40 is biased, in an upward direction, by a pressure difference (P1−Pp)between the upstream-side pressure P1 and the intermediate pressure Pp.Thereby, the first valve section of the main valve 6 is closed and thesecond valve thereof is opened. As a result, the second passage isopened as shown in FIG. 1, thus achieving the closed state of the firstpassage. In other words, the refrigerant introduced from the lead-inport 14 is led out from the lead-out port 18.

When, on the other hand, the solenoid 4 is turned on, the suction forceis created by the solenoidal force in between the plunger 84 and thecore 80, as shown in FIG. 2. Thus, the pilot valve element 98 is biasedin a valve closing direction and then the pilot valve 8 is closed.Since, at this time, the refrigerant fed from the upstream side is ledinto the back pressure chamber 66 through the leakage passage 74, theintermediate pressure Pp becomes the upstream-side pressure P1. At thistime, the pressure of the refrigerant acting on the driven member 40 hasalready been canceled out and therefore the driven member 40 is smoothlydriven by the solenoidal force. As a result, the first valve section ofthe main valve 6 is quickly opened and the second valve section thereofis closed. In other words, as shown in FIG. 2, the opening of the firstpassage achieves the closing of the second passage and, as a result, therefrigerant introduced from the lead-in port 14 is led out from thelead-out port 16.

A detailed description is now given of characteristic and distinctivestructures and operations of the control valve 1.

FIG. 3 is a partially enlarged view showing a fall prevention structureof a sealing member in a valve element. FIG. 4 schematically shows aprocess of assembling a sealing member. FIGS. 5A and 5B each shows astructure of a support member before the support member is assembled.FIG. 5A shows a support member viewed in a direction of arrow C of FIG.4, and FIG. 5B shows a support member viewed in a direction of arrow Dof FIG. 4.

As shown in FIG. 3, the support member 52 is of stepped disk shape suchthat the outside diameter of an upper half thereof is smaller than theoutside diameter of a lower half thereof. As shown in FIG. 5A, anannular recess 130, into which the packing material 56 is fitted, isformed on the top face of the support member 52. The packing material 56has an annular shape that is substantially complementary to the shape ofthe recess 130, and is assembled in such a manner as to be fitted intothe recess 130. A bottom face of the recess 130 is a supporting surface134 that supports the packing material 56 from below. Also, an upper endopening part of the support member 52 is swaged inward and becomes anengagement part 136 that supports an outer peripheral edge part of thepacking material 56 from above.

An inner peripheral edge part of the packing material 56 is supportedfrom above by a flange portion 138 that protrudes radially outward on alower portion of the body 42. A sealing surface 140 of the packingmaterial 56 is exposed to between the engagement part 136 and the flangeportion 138. The valve element 44 touches and leaves the valve seat 28on the sealing surface 140. Since the packing material 56 is made of amaterial that swells on exposure to the refrigerant, an appropriateclearance (backlash) is provided, in a radial direction, between thepacking material 56 and the recess 130. Provision of such clearance canabsorb the amount of expansion in the event the packing material 56swells.

A ring-shaped flow passage 142, which is circularly open on thesupporting surface 134, is formed in the support member 52. Also, acommunicating path 144, which is used to communicate between thisring-shaped flow passage 142 and the valve chamber 38, is provided inthe support member 52. The communicating path 144 extends from thering-shaped flow passage 142 in a radial direction and is open on a sidesurface of the support member 52. The ring-shaped flow passage 142 andthe communicating path 144 each functions as a “fluid flow passage” thatis used to ensure the flow of refrigerant between a side surface of thepacking material 56 opposite to the sealing surface 140 (i.e., a contactface of the packing material 56 with the supporting surface 134) and thevalve chamber 38. It is to be noted here that the ring-shaped flowpassage 142 is open farther radially outward than a position where thepacking material 56 touches and leaves the valve seat 28 (see adashed-dotted line in FIG. 3) and is open more radially inward than atip end position of the engagement part 136 (see a dashed-two dottedline in FIG. 3).

Similarly, as shown in FIG. 5B, an annular recess 150, into which thepacking material 58 is fitted, is formed on the bottom face of thesupport member 52. The inside diameter and the outside diameter arelarger than the inside diameter and the outside diameter of the recess130, respectively. The packing material 58 has an annular shape that issubstantially complementary to the shape of the recess 150, and isassembled in such a manner as to be fitted into the recess 150. A bottomface of the recess 150 is a supporting surface 154 that supports thepacking material 58 from above. Also, a lower end opening part of thesupport member 52 is swaged inward and becomes an engagement part 156that supports a peripheral edge part of the packing material 58 frombelow.

An inner peripheral edge part of the packing material 58 is supportedfrom below by the guide member 54. A sealing surface 160 of the packingmaterial 58 is exposed to between the engagement part 156 and the guidemember 54. The valve element 44 touches and leaves the valve seat 36 onthe sealing surface 160. Since the packing material 58 is made of amaterial that swells on exposure to the refrigerant, an appropriateclearance is also provided, in a radial direction, between the packingmaterial 58 and the recess 150.

A ring-shaped flow passage 162, which is circularly open on thesupporting surface 154, is formed in the support member 52. Also, acommunicating path 164, which is used to communicate between thisring-shaped flow passage 162 and the valve chamber 38, is provided inthe support member 52. The communicating path 164 extends from thering-shaped flow passage 162 in the direction of axis line and is openon a side surface of the support member 52. The ring-shaped flow passage162 and the communicating path 164 each functions as a “fluid flowpassage” that is used to ensure the flow of refrigerant between a sidesurface of the packing material 58 opposite to the sealing surface 160(i.e., a contact face of the packing material 58 with the supportingsurface 154) and the valve chamber 38. It is to be noted here that thering-shaped flow passage 162 is open farther radially outward than aposition where the packing material 58 touches and leaves the valve seat36 (see a dashed-dotted line in FIG. 3) and is open more radially inwardthan a tip end position of the engagement part 156 (see a dashed-twodotted line in FIG. 3).

The valve element 44 configured as above is assembled as shown in FIG.4. In other words, the packing material 56 is first fitted into therecess 130 of the support member 52 and then the upper end opening partof the support member 52 is swaged inward so as to fix the packingmaterial 56. Also, the packing material 58 is fitted into the recess 150of the support member 52 and a lower end opening part of the supportmember 52 is swaged inward so as to fix the packing material 58 (see adashed-line arrow in FIG. 4). An assembling body and the guide member54, which both have been obtained as above, are sequentially assembledin such a manner as to be inserted around the body 42 from below, andthen a low end opening part of the body 42 is swaged outward so as tofix the assembling body and the guide member 54 (see solid arrow in FIG.4).

The above-described supporting structures for the packing materials 56and 58 function as the fall prevention structures for the respectivepacking materials. In other words, by employing the above-described fallprevention structures, the fluid flow passage comprised of thering-shaped flow passage 142 and the communicating path 144 is formed inthe support member 52. Thereby, a side of the packing material 56opposite to the sealing surface 140 is constantly communicated with theupstream passage, and this state of constantly communicating with eachother remains in effect. This makes it difficult for the pressuredifference to work on the top and the bottom face of the packingmaterial 56. As a result, no force sufficient to separate the packingmaterial 56 from the recess 130 occurs. Hence, the packing material 56can be prevented from falling off from the support member 52.

In more detail, since the upstream-side pressure P1 (high pressure) actson the sealing surface 140 of the packing material 56, too, at the timethe first valve section is closed as shown in FIG. 3, the pressures onthe top face and the bottom face of the packing material 56 aregenerally remained well-balanced. Besides, the packing material 56 issubjected to a pressing force from the valve seat 28 and therefore thepacking material 56 will not fall off from the recess 130. When, on theother hand, the open/close status of the first valve section transitsfrom “closed” to “open”, the valve seat 28 gets spaced apart from thepacking material 56 and the pressure acting on the sealing surface 140drops rapidly. At the same time, however, the pressure acting on theside surface (back side) of the packing material 56 opposite to thesealing surface 140 thereof is also promptly reduced via the fluid flowpassage. Hence, no force sufficient to separate the packing material 56from the recess 130 occurs. In other words, provision of the fluid flowpassage can release a high-pressure refrigerant, which has entered a gapbetween the packing material 56 and the support member 52 (namely, theresidual pressure due to the high-pressure refrigerant can be eliminatedquickly). This can prevent the packing material 56 from falling off fromthe support member 52. Such operation and advantageous effects asdescribed above can be similarly achieved for the packing material 58,too, at the time the second valve section is opened/closed but therepeated description thereof is omitted here.

FIGS. 6A and 6B are each a partially enlarged view of a seal structurein a piston of a driven member. FIG. 6A shows a structure around thepiston, and FIG. 6B shows a process of assembling the piston. FIGS. 7Aand 7B are each a perspective view showing a structure of a component ofthe piston. FIG. 7A shows a piston ring, and FIG. 7B shows a tensionring.

As shown in FIG. 6A, the piston 46 is configured such that the pistonring 72 is held between the piston body 68 and the support 70. Thepiston body 68 has a larger-diameter part 168, around which the pistonring 72 is inserted, and a smaller-diameter part 170, around which thesupport 70 is inserted. A flange portion 172 is formed connectedly on anupper portion of the larger-diameter part 168. Also, the support 70 hasa ring-shaped body 174, which is inserted around the smaller-diameterpart 170, and a flange portion 176, which extends radially outward froman upper portion of the body 174. An upper end of the spring 76 issupported by the flange portion 176. When the piston 46 is to beassembled, the tension ring 78, the piston ring 72 and the support 70are sequentially assembled relative to the piston body 68, as shown inFIG. 6B.

As shown in FIG. 6A, a height h1 of the larger-diameter part 168 isslightly smaller than a height h2 of the piston ring 72. The height ofthe tension ring 78 is slightly smaller than the height h2 of the pistonring 72. As a result, a predetermined clearance CL is formed between thepiston body 68 and the support 70, in the direction of axis line.Provision of the clearance CL allows the piston ring 72 to reliably abutagainst the flange portion 172 on an upper end surface of the pistonring 72 and allows the piston ring 72 to reliably abut against theflange portion 176 on a lower end surface thereof. In other words, thepiston ring 72 is reliably held by the piston body 68 and the support70.

As shown in FIG. 7A, the piston ring 72 is ring-shaped such that one endthereof in the peripheral direction is engaged with the other endthereof in the peripheral direction. Thereby, the piston ring 72 isconfigured such that it is deformable in the radial direction by up to apredetermined amount. As shown in FIG. 7B, the tension ring 78 has aC-shape cross section and is constituted by a plate spring thatgenerates a biasing force radially outward. When the piston 46 havingconfigured as described above is assembled as shown in FIG. 6A, thetension ring 78 presses the piston ring 72, from within, radiallyoutward. This creates an appropriate sliding force in between the pistonring 72 and the guiding passage 73.

FIG. 8 is a graph showing an operation and advantageous effects of aseal structure in a piston. The horizontal axis of FIG. 8 indicates apressure difference ΔP acting on the piston 46 (i.e., the pressuredifference (P1−Pp) between the high-pressure chamber 64 and the backpressure chamber 66). And the vertical axis thereof indicates a leakageamount of refrigerant from the high-pressure chamber 64 toward the backpressure chamber 66 through a gap between the piston 46 and the guidingpassage 73. The solid line in FIG. 8 indicates a result of the presentembodiment, whereas the dashed-dotted line therein indicates a result ofa comparative example. The comparative example is of a conventionalstructure such that the piston is not divided into the piston body andthe support.

By employing the present embodiment, the piston 46 is configured asdescribed above, so that, as shown in FIG. 8, the leakage amount ofrefrigerant can be significantly reduced in a domain where the pressuredifference ΔP is small to a domain where the pressure difference ΔP islarge. In contrast to the present embodiment, the amount of refrigerantin the comparative example is large in the domain where the pressuredifference ΔP is small. This may be deduced for the following reasons.That is, as shown in FIG. 6A, the present embodiment is configured suchthat the piston 46 is divided into the piston body 68 and the support70, such that the piston ring 72 is held between the piston body 68 andthe support 70, and such that a clamping force by which the piston ring72 is held therebetween can be obtained by not only the pressuredifference (P1−Pp) but also the biasing force of the spring 76. Thus,even when, in particular, the pressure difference (P1−Pp) is small, thetop face and the bottom face of the piston ring 72 can be firmlyattached to the piston body 68 and the support 70, respectively. Thissuppresses the leakage of refrigerant through a gap in the fitting spaceof the piston ring 72 in the piston 46.

In contrast, the clamping force as in the present embodiment cannot beobtained for the piston ring in the comparative example. Thus, thepiston ring in the comparative example is loosely fit when, inparticular, the pressure difference (P1−Pp) is small. As a result, therefrigerant is more likely to leak in the comparative example through agap or gaps of a fitting space. In other words, the present embodimentis of such a structure that the problem like this in the comparativeexample can be resolved.

FIGS. 9A and 9B are each a partially enlarged view showing a stopperstructure in a pilot valve. FIG. 9A shows a state where the pilot valveis open (see a dashed-dotted circle in FIG. 1), and FIG. 9B shows astate where the pilot valve is closed (see a dashed-dotted circle inFIG. 2).

As shown in FIG. 9A, a lower end opening part of the valve formationpart 114 is swaged inward in the pilot valve element 98, therebyconstituting the stopper 118. The stopper 118 supports, from below, anouter peripheral edge part of the sealing member 112 contained in thefitting space 116. A sealing surface 180 of the sealing member 112,which is exposed on an underside thereof, touches and leaves the pilotvalve seat 51 so as to close and open the pilot valve 8, respectively.After the sealing member 112 has started seating on the pilot valve seat51, the stopper 118 is stopped by an upper end surface of the body 42and thereby the displacement of the pilot valve element 98 caused by thedeformation of the sealing member 112 is restricted.

The pilot valve seat 51 having a circular boss shape is formed, in aprotruding manner, on a central part of the upper end surface of thebody 42. The pilot valve seat 51 is configured such that a part thereoffrom the upper end surface of the body 42 to a height h3 is a taperedportion 182 where the cross section thereof is gradually reduced upward.And the pilot valve seat 51 is configured such that the upper portionthereof above the tapered portion 182 is an attaching/detaching portion184 whose cross section is constant (the outside diameter is constant).In this configuration as described above, a height h4 of the stopper 118is set larger than the height h3 of the tapered portion 182. As shown inFIG. 9B, this configuration allows the sealing surface 180 of thesealing member 112 not to reach the tapered portion 182 at the time thepilot valve 8 is closed. In other words, the sealing member 112 hasflexibility and therefore the pilot valve seat 51 bites in the sealingmember 112, which is elastically deformably pressed by the pilot valveseat 51, when the pilot valve 8 is closed; however, the degree to whichthe pilot valve seat 51 bites in the sealing member 112 can be setwithin an extension range of the attaching/detaching portion 184. As aresult, a pressure-receiving diameter E of the pilot valve element 98can be constantly set equal to the outside diameter of theattaching/detaching portion 184.

Further, a plurality of communicating paths 186 are formed, atpredetermined intervals, in a circumferential direction on a bottom faceof the stopper 118. The communicating paths 186, which are so providedas to extend in a radial direction, communicate between a space,surrounded by the stopper 118 and the pilot valve seat 51, and the backpressure chamber 66, when the stopper 118 is stopped by the body 42 asshown in FIG. 9B. Such configuration and arrangement as described aboveallow the pressure-receiving diameter E of the pilot valve element 98 toremain constant from the start when it abuts against the pilot valveseat 51 until when it is stopped.

As described above, the configuration and arrangement of the stopper 118and the pilot valve seat 51 are devised. This can accurately set theamount of displacement developed by the pilot valve element 98 inclosing the pilot valve 8. As a result, the magnetic gap between thecore 80 and the plunger 84 at the time the valve is closed can remainconstant. Also, the pressure-receiving diameter E of the pilot valveelement 98, when it seats on the pilot valve seat 51, can remainconstant. This can prevent the occurrence of noise caused when the core80 and the plunger 84 hit each other. Also, the value of currentsupplied to the solenoid 4, which is required to close not only thepilot valve 8 but also the second valve section can be kept constant andtherefore the control performance of the solenoid 4 is stabilized.

The description of the present invention given above is based uponillustrative embodiments. These embodiments are intended to beillustrative only and it will be obvious to those skilled in the artthat various modifications could be further developed within thetechnical idea underlying the present invention.

FIGS. 10A and 10B are each a partially enlarged view showing a structureof a seal structure in a piston of a driven member according to amodification. FIG. 10A shows a structure around the piston, and FIG. 10Bshows a process of assembling the piston.

In the present modification, the shape of a support 270 is so devisedthat the tension ring 78 shown in FIGS. 6A and 6B is omitted. In otherwords, a tapered surface 280 is formed on a flange portion 276 of thesupport 270, and the support 270 is brought close to the piston body 68;thereby, the piston 246 is configured such that a biasing force in aradially outward direction is applied to the piston ring 72 by thetapered surface 280. In this modification, too, a predeterminedclearance CL is formed between the piston body 68 and the support 270,in the direction of axis line. When the piston 246 is to be assembled,the tension ring 78, the piston ring 72 and the support 270 aresequentially assembled relative to the piston body 68, as shown in FIG.10B. By employing the configuration and arrangement according to thepresent modification, the leakage amount of refrigerant can besignificantly reduced over the domain where the pressure difference ΔPis small to large.

In the above-described embodiments, the material that constitutes thepacking materials 56 and 58 (sealing members) is rubber. The materialconstituting the sealing member 112 is rubber as well. In amodification, other flexible materials, such as polytetrafluoroethylene(PTFE), may be used. In the above-described embodiments, the materialconstituting the body 42 of the driven member 40 is made of an aluminumalloy, and the material constituting the body 110 of the pilot valveelement 98 is made of stainless steel (SUS). In a modification, both thebody 42 thereof and the body 110 thereof may be made of the samematerial. In that case, the same material constituting both of them maybe an aluminum alloy or stainless steel, or a material including anothermetal or the like may be used. In the above-described embodiments, thematerial constituting the piston ring 72 is made ofpolytetrafluoroethylene (PTFE) but, instead, a material including otherresin materials, carbon, metal or the like may be used.

In the above-described embodiments, the description has been given of anexample where the ring-shaped flow passages 142 and 162 are formed inthe support member 52. In a modification, the ring-shaped flow passage142 may be provided in the packing material 56 and may communicate withthe communicating path 144 provided in the support member 52. Similarly,the ring-shaped flow passage 162 may be provided in the packing material58 and may communicate with the communicating path 164 provided in thesupport member 52.

In the above-described embodiments, the description has been given of anexample where the ring-shaped flow passages 142 and 162 are each formedin a single circular shape. Instead, an intermittent (discontinuous)flow passage may be arranged circularly along a virtual circle. In thatcase, a communicating path is provided in each flow passage and is madeto communicate with the valve chamber 38.

In the above-described embodiments, the description has been given of anexample where the packing materials 56 and 58 (sealing members) areswaged and joined to the support member 52 and where the sealing member112 is swaged and joined to the valve formation part 114. In amodification, at least one or some of the sealing members may be clampedusing screws, for instance, and may be joined using a means and/orprocess other than the swaging.

In the above-described embodiments, the description has been given of anexample where the configuration and arrangement are such that thestopper 118 is provided at the tip of the pilot valve element 98 and isstopped by the driven member 40. In a modification, the stopper 118 maybe stopped by other members such as the third body 13. Also, the stoppermay be provided in a middle part of the pilot valve element 98 in alongitudinal direction and may be stopped by the core 80 or the thirdbody 13. In that case, too, it is presupposed that the sealing member112 touches and leaves the pilot valve seat 51 within the extensionrange of the attaching/detaching portion 184.

In the above-described embodiments, the description has been given of anexample where the control valve 1 is configured as a three-way valvehaving two lead-out ports for a single lead-in port. Instead, thecontrol valve 1 may be configured as a two-way valve, for example,having one lead-out port for a single lead-in port. Or alternatively,the control valve 1 may be configured as a four-way valve having twolead-out ports for two lead-in ports. The valve element where thesealing member is fitted may be provided upstream of the valve section,similarly to the above-described embodiments.

In the above-described embodiments, the description has been given of anexample where the control valve 1 is configured as an electromagneticvalve provided with the solenoid that functions as an actuator forelectrically regulating the opening degree of the valve section from theoutside. Instead, the control valve 1 may be configured as otherelectrically driven valves, such as a motor-operated valve provided witha motor that functions as the actuator, for instance. Also, adescription has been given of an example where the control valveaccording to the preferred embodiments is applied to an air conditionerof an electric-powered vehicle but it goes without saying that thecontrol valve is applicable to an air conditioner of a vehicle providedwith an internal-combustion engine and an air conditioner of a hybridvehicle equipped with both an internal-combustion engine and an electricmotor drive. Further, the control valve according to the preferredembodiments is applicable to not only the vehicles but also anyapparatuses and devices equipped with the electrically driven valve.Also, the control valve according to the preferred embodiments isapplicable to an apparatus or system where a fluid, such as water oroil, other than the refrigerant flows is applicable.

The present invention is not limited to the above-described embodimentsand modifications only, and those components may be further modified toarrive at various other embodiments without departing from the scope ofthe invention. Also, various other embodiments may be further formed bycombining, as appropriate, a plurality of structural componentsdisclosed in the above-described embodiments and modification. Also, oneor some of all of the components exemplified in the above-describedembodiments and modifications may be left unused or removed.

What is claimed is:
 1. A pilot operated electromagnetic valvecomprising: a body having a lead-in port through which a fluid is ledin, a lead-out port through which the fluid is led out, and a mainpassage joining the lead-in port to the lead-out port; a metallic drivenmember integrally formed with both a main valve element and a partition,wherein the main valve element opens and closes a main valve by touchingand leaving a main valve seat provided in the main passage and whereinthe partition separates the main passage from a back pressure chamber; apilot valve element opens and closes a pilot valve by touching andleaving a pilot valve seat, the pilot valve seat being provided in asub-passage joining the lead-in port to the lead-out port by way of theback pressure chamber; and a solenoid including a first iron core, whichis displaced integrally with the pilot valve element in a direction ofaxis line, and a second iron core, which faces the first iron core inthe direction of axis line, wherein a pilot passage is formed in suchmanner as to pass through the driven member, the pilot valve seat isprovided at one end side of the pilot passage such that the pilot valveseat protrudes toward the back pressure chamber, and the other end ofthe pilot passage communicates with the lead-out port, wherein the pilotvalve element includes: a metallic pilot valve body formed integrallywith the first iron core; a flexible sealing member, fitted on a tip ofthe pilot valve body, which touches and leaves the pilot valve seat; anda stopper for restricting a displacement of the pilot valve elementrelative to the driven member in a manner such that the stopper isstopped in the direction of axis line after the sealing member hasseated on the pilot valve seat, and wherein the stopper is configuredsuch that a pressure-receiving diameter of the sealing member, whichreceives a pressure difference between an upstream side and a downstreamside of the pilot valve, remains unchanged from when the sealing membercomes in contact with the pilot valve seat until when the sealing memberhas completely seated on the pilot valve seat with the result that thestopper is stopped by the driven member.
 2. An electromagnetic valveaccording to claim 1, wherein the stopper is provided at a tip of thepilot valve body and is stopped by the driven member.
 3. Anelectromagnetic valve according to claim 1, wherein a communicatingpath, which communicates between a space, surrounded by the stopper andthe pilot valve seat, and the back pressure chamber, is formed when thestopper is stopped by the driven member.
 4. An electromagnetic valveaccording to claim 2, wherein a communicating path, which communicatesbetween a space, surrounded by the stopper and the pilot valve seat, andthe back pressure chamber, is formed when the stopper is stopped by thedriven member.